If you deny to anyone else the right to say what you think is wrong, it will not be long before you will lose the right to say what you think is right.

Defense of the freedom of others is self-defense.

"I disapprove of what you say, but I will defend to the death your right to say it" acknowledges the fundamental right of every individual to express their thoughts and ideas without fear of censorship or retribution, regardless of whether we agree with them or not.